Method of manufacture of abrasive devices



Oct. "16, 1928. 1,687,770

I M. C. HUTTOI .METHbD OF MANUFACTURE OF ABRASiVE DEVICES Filed June 18, 1926 2 Sheefis-Sheek 1 Oct. 16, 1928.

M. C. HUTTO METHOD OF MANUFACTURE OF ABRASIVE DEVICES Filed June 18. 1926 2 Sheets-Sheet INVENTOR NA/PwZ/V C f/urm ATTORNEY.

I I 3 l Patented Get. 16, 1928.

urrso STATES MARSDEN C. HUTTO, 0F DETROIT, MICHIGAN.

METHOD OF MANUFACTURE OF ABRA'SIVE DEVICES.

Application filed June 18,

This invention relates to an improved method of manufacture of abrasive devices of various types, such as grinding stones for use in internal grinders or grinding wheels and various other types of manufactured abrasive devices formedof a composition of material includng an abrasive and a binder commonly in use.

The purpose of the invention is to provide a method of manufacture whereby the finished abrasive device is of practically unlform hardness throughout. \Vith abrasive devices as usually made the material is not of uniform hardness resultng in soft spots whereby the stones will wear more rapidly at one point than another and require continual dressing to secure the necessary uniform surface shape. I have discovered that th1s soft ness occurs in the usual manufactured article as heretofore made by reason of the material not being compacted to an equal degree so that. when it is submitted to PIBSSUI'QYIII. the mold or form provided therefor, the portlons of less compactness are not submitted to the same pressure as those portions that are more compact. This inequality in the hardness of the stones of various forms has previously been attributed mainly to non-uniformity of the mixture. I have discovered that this is in error and the non-uniformity in the hardness and wearing quality of the stone is produced directly by reason of inequality in the compactness of the material before submissionto pressure in the mold.

Abrasive devices of the character herein described are usually formed of an abrasive material as for instance silicon carbide and a binder and additional chemical constituents including a small percentage of moisture. This material is well known in the art and the actual constituents of the stone are not involved in this invention. This material is in a ground form and the fineness depends upon the quality or' texture of the stone to be produced and ordinarily is placed in a mold and subjected to the necessary pressure and then is tired in a kiln similar'to a ceramic kiln. 1 have found that, in placing of the material in a mold the workman in resting his hands upon some portion of it or in some other way will compact the material at some point or oints to a degree greater than at some other portion of the surface which results in the stone having soft and hard spots as above mentioned. My process seeks to ch- 1926. Serial No. 116,835.

viate this difficulty enabling the workman to place material in the mold as usual and in which some portions may be compacted to a degree greater than others and still produce a stone that is of uniform hardness. In the carrying out of this process some means is required to submit the entire area of the material to an equal pressure and the accompanying drawings are illustrative of a machine adapted to perform this function.

Such a machine is shown in the accompany in drawings in which T ig. 1 is a front elevation thereof.

Fig. 2 is a side elevation.

Fig. 3 is a view of the form in which the material is compacted,

It is to be understood that any mechanism or means by which the material may be compacted uniformly previous to submission to pressure may be utilized. The drawing merely illustrates a hand-operated device used in the performance of this step of the process. This machine consists of a main frame 1 having the two uprights 2 and 3 and cross member 4 at the top apertured to receive the tamping bars 5. Adjacent the lower or tamping end of these bars, each is provided with an elongated slot 6 in which is positioned a rod 7 extending across the machine, the uprights 2 and 3 being apertured to permit the rod to extend therethrough. This rod is supported adjacent each side frame by a pivoted arm 8, 8. A coiled spring 29-connected with each arm tends to raise the rod and therefore to lift the tamping bars upon the rod engaging the upper end of the slot. These bars lie in alignment in the machine here shown which is adapted to produce a comparatively narrow rectangular stone with the mold illustrated. The mold may be of any particular character here shown as being formed of two end members ,9 and 10 and the longitudinal connecting members 11 and 12 spaced apart at the center as shown. In this central space bars 15 and 16. On the upper surface of this mold I provide a small hopper indicated generally at 17 formed of two parts hinged as shown clamped together at one'endby means of a screw clamp 18. The mold is positioned between the side members of the frame and directly beneath the ends of the tamping bars after being filled with the granular material by hand or in any approved manner. By pressing downward on the'rod 7 the bars are allowed to move downwardly by gravity and the slot in the bars is Y sufficiently long to enable the rod to be retracted from contact with the upper side thereof so that each bar rests freely and by gravity upon the material in the mold.

These bars are exactly alike in weight either i being formed in a mold or subsequently machined or otherwise finished in such manner that they are practically exactly equal in weight. In the machine shown the bars are spacedapart'a distance equal to their Width longitudinally of the mold andin the use of this machine the tamping bars are first low- .ered to position on the filled mold and hopper so that each of the points contacted byatamping bar is subjectedto equal pressure andthe tamping bars are then lifted and the mold box (which is less in length than the distance between the side bars 2 and 3 of the machine) is moved endwise so that the spaces between the'bars not tamped in the first opera-tion are brought to registration with the ends correspondingly differ in the arrangement of its parts while the function thereof remains the same. The mold box in the machine shown is limited in its movement'by means .of screws 19 and 20 in the respective side members of the frame so that inplacing the mold imposition in contact with one screw at one end or the other the proper registration of the mold and tamping hers is secured but any arrangement of mold and frame to secure the desiredregistration with the tamping bars'to insure each small ,area being tamped may be used. It is to be noted that this mold and hopper may be filled in any ordinary way as by hand and in the performance-of the process it is not at all .im-. portant as to whether or not some portions of the material are pressed into the mold with greater pressure than some other parts unless the pressure be'excessive or in excess of the weight of the individual tamping bars'which would be'quite unusual and would require adefinite action on the part of the workman to secure such a result. Ordinarily in the mere filling of the mold by hand even though some portions of the material are pressed to a. degree greater than some of the parts the lowering of the tamping bars to the position so'that the weight of the same is caused to exert pressure upon the surface practically throughout its whole area, those points or spots of material in the mold that are naturally of less compactness than others will be brought to the same degree of compactness by the pressure of the tamping bars. The result usually is that the bars at the ,end of the mold are moved downwardly to an extent greater than .those at the center of the mold as is s g ested, in Fig. 3, and that the surface of thefinaterial after being compacted by the tamping bars still lies above the upper surface of the v die block and in the hopper. Subsequent to the tamping operation the hopper is removed, it being merely retained dowel pins one of which is indicated seal on the surface of the mold. After removal of the hopper the mold is struck off at the upper surface leaving it filled with material of equal compactness throughout its a'realiThis mold after being struck off, as stated, is placed in any convenient machine, as a press and the material in the mold compressed to the required degree to produce the desired hardness of the stone. Itis to be understood that the pressure to which the molded material is subjected after being first compacted, as stated, depends very largely upon the character of the stone to be manu; factur edthat is, if a stone of eX-tremeliardness is desired it is submitted to a greater pressure and if less hardness isdesired correspondingly less pressure is utilized. After being submitted to the final pressure as stated,

the stone is fired in a kiln in the usual way and subsequently utilized forthe purpose for which it is designed. v

The essential feature of the process is in the step of first compacting the material to an equal degreeover its entire area previous to submitting to the pressure by which the final hardness of the stone is largely determined. This process so far as my knowledge extends, has never been utilized in the manuno so called soft spots andtherefore will Swear economically in use without particular quality is uniform throughout the entire stone which-may be worn to its'limit of wear without any change in its uniformity; I am 'facture of'an abrasive deviceof any type and .by such step the finished abrasive device has therefore able to provide an abrasive device with a much longer life than has heretofore formation of the articles of this type for the been possible, that has the uniformity of hardness so greatly desired by users that to a very material extent reduces the dressing of thedevice to a minimum during its period of use to maintam a uniform surface shape.

One of the difiicultiesat present encountered in this art is that grinding stones or Wheels are designated by a grade known to vary greatly in their hardness, although they may havebeen submitted to a pressure over the whole surface that determines the grade.

This inequality in grade arises as before stated by reason of the fact that the material,

before being subjected to the pressure de- 5 termining its final hardness, is not uniformly compacted. This process therefore eliminates waste both in use andin manufacture and there is no loss of stones in manufacture due to imperfectness as to grade hardness as is the case under methods at present in use,

The process, as above described, contem-- plates the manufacture'of an abrasive device which requires to be fired in a kiln but there are abrasive devices that do not require final firing'and this processis of equal value in the reason that uniform hardness of wearing surface and uniform hardness of the bodyls as desirable as in that class of articles which re- "quire the final step of firing. Thus, the proc- "ess is adaptable for use with various articles formed of a granular material and is adapted 1 for use in compacting granular material not of an abrasive character but in which uniformity in compactness is a necessary feature, and experience has established that this uniformity of compactness of the article of whatever character formed of a granular material is in the step of first subjecting it while in a mold form to an equal light degree of pressure throughout small 'areas whose total equals the total area of the article and then subjectingthis lightly compacted material to a greater pressure. The method at present in use in various'articles formed of granular material contemplates the subjecting of the whole area at one stroke or at one time to pressure. This method now in use is made quate due to the fact that the parts of mate rial more highly compacted in the placing in the mold prevent theplunger or means used to exert pressure thereon to exert itspress ure uniformly. By using a plunger formed of a large number of smallparts each acting independently of the other the whole surface may be compacted at one time andto' an-iequal degree after the general manner described.

Having thus fully describedmy process, what I claim and desire to secure by Letters Patent of the United States is 1 1. The method of manufacture'of an abrasive device from granular material of the desired composition which consists in first -filling a mold with the'material, then tamping small areas of the njaterial individually to a substantially equal degree of pressure, striking off the mold, submitting the molded material to a greater degree of pressure, and finally firing the molded article.

2. The method of manufacture of abrasive devices of ground material of'the desired fineness and composition consisting in first filling a mold with material, then subjecting the same to pressure in independent small areas over the entire surface sothat the e11- tire area has been compacted to an equal dein the mold to a higher pressure. and then firing the article thus formed. v

3. The method of manufacture of abrasive devices from granular material of the desired fineness and composition, the step consisting in submitting small-areas of the material to an equal pressure, the total of the small areas being equivalent to the surface area of the device, and-then submitting the entire area to a higher pressure to produce the final desired compactness,,and then firing the article.

4. The method of forming an abrasive device from granular material of the desired .gree, then submitting the compacted article character and composition. which consists in placing the same in the mold, compacting the material in the said mold to a slight degree of pressure in such manner that the material is compacted to substantially equal degree throughout the body thereof, then submitting the compacted material to a-high degree of pressure uniformly over its surface, and finally firing the formed article.

5. The method of forming an'abrasive device which consists in preparation of the material in a granular form of the desired fineness and composition, placlng the same in a mold of separable parts having a depth greater than the desiredthickness of the fin-- ished article, subjecting the surface of the material while in the mold to equal pressure throughout small areas thereof in such manner that the entire surface area of the material has been subjected to an equal pressure and the material in the mold is. of substanwith material of the desired fineness and composition and to a depth greater than the final thickness of the article, then subjecting the material to comparatively light pressure through comparatively small areas so that theentire surface is subjected at said areas to an equal degree of pressure and the material in the mold compacted to an' equal degree throughout its body, then cutting oil the upper surface of the compacted material so that the material remaining in the mold is of uniform depth, then subjecting the compacted material to ahigher degree of pressure.

7. In a methodof preparing granular material to form an article of equal hardness throughout its body which consists in placing the material of the desired composition in a mold, the depth of which is greater than the thickness of the article to be formed, then compacting the material in the mold by subjecting the surfacethereof at a plurality of small areas equaling approximately the area of the article to be formed to a slight degree of pressure so that the material is first compacted to a slight degree to an equal extent throughout the entire body, removing the upper portion of the compacted material to provide a level upper surface, and then subjecting thismaterial over the entire exposed surface in themold to a materially higher this material individually under substantially equal degrees of pressure, then striklng as the mold, and then submitting the material in the mold to a greater degree of pressure.

9: The herein described method of produc-"- ing an abrasive device from granular material which consists in filling a mold with the material, then tamping'smallareas of this material individually by means of tamping' members which are adapted to press by their weight only against the granular material,

mold, and then submitting the remaining material in the mold to a greater degree of pres? sure.

In testimony whereof I sign thisspecifica tion. p

MAR SDEN C. HUTTO.

then striking oil the granular material in the I 

